connectPorts only adds a producer to threadableStages, if it has not
been added yet

Prework 2.0

See merge request !46

moved javadoc to the public class

Prework 2.0

Some minor things which needed to be done before 2.0

See merge request !45

Conflicts:
	src/test/java/teetime/framework/RunnableConsumerStageTestConfiguration.java

both uses the context now

Connector survey

See merge request !44

added null checks

Conflicts:
	src/main/java/teetime/framework/pipe/InstantiationPipe.java